Mullite ceramics were fabricated by a reaction-bonding technique from the powder mixtures of Al2O3 and Si with an Y2O3 addition. The effects of the initial powder composition on the mullitization and densification behaviors were investigated. It has been shown that mullitization and densification can be simultaneously enhanced by a low-viscosity yttrious silicate glass. After a 2 h heating at 1400 degreesC, all the specimens exhibited a dense microstructure. Moreover, mullite grains were observed to have an elongated morphology, while the yttrious silicate glass was found to crystallize into Y2Si2O7 at the later stages of mullite growth. (C) 2002 Published by Elsevier Science B.V.